Sodium alginate Chemical Properties,Uses,Production

Description

Sodium alginate is the sodium form of alginate. Alginate is a
linear, anionic polysaccharide consisting of two form of 1, 4-linked
hexuronic acid residues, β-d-mannuronopyranosyl (M) and α-l-
guluronopyranosyl (G) residues. It can be arranged in the form of
blocks of repeating M residues (MM blocks), blocks of repeating G
residues (GG blocks), and blocks of mixed M and G residues (MG
blocks). Commercially available alginate currently originates from
algae. Alginate has wide applications. For example, one of its most
important role is being used as wound dressing materials for the
treatment of acute or chronic wounds. The use of alginate
crosslinking to make hydrogels for cell encapsulation is also quite
valuable. The emergence of various kinds of its derivatives recently
has further extended its application.

Chemical Properties

solid

History

Sodium alginate is a natural polysaccharide product that was first described in a patent application by the British chemist Edward C C Stanford in 1881. To this day brown algae are still the main source used to extract sodium alginate from. This group includes many of the seaweeds, like kelps, found in chilly northern seas. In addition to the food industry, the gelling properties of sodium alginate have been used in medical, dental and cosmetic applications for years.

Uses

Sodium alginate can be used as a flavorless gum. It is used by the foods industry to increase viscosity and as an emulsifier. It is also used in indigestion tablets and the preparation of dental impressions.

Sodium alginate (NaAlg) and its modified forms have been widely used as membranes in pervaporation (PV) separation of aqueous‐organic solutions because of the hydrophilic nature and versatility to modify/tune their structures to achieve the desired separation.

Sodium alginate is a polymer which can be extracted from brown seaweed and kelps. It is one of the structural polymers that help to build the cell walls of these plants. It has some unusual properties and a wide variety of uses.
The polymer can be represented like this:
When sodium alginate is put into a solution of calcium ions, the calcium ions replace the sodium ions in the polymer. Each calcium ion can attach to two of the polymer strands. This is called cross-linking and can be represented like this:

Uses

In the manufacture of ice cream where it serves as a stabilizing colloid, insuring creamy texture and preventing the growth of ice crystals. In drilling muds; in coatings; in the flocculation of solids in water treatment; as sizing agent; thickener; emulsion stabilizer; suspending agent in soft drinks; in dental impression preparations. Pharmaceutic aid (suspending agent).

Purification Methods

Free it from heavy metal impurities by treatment with ion-exchange resins (Na+-form), or with a dilute solution of the sodium salt of EDTA. Alternatively dissolve it in 0.1M NaCl, centrifuge and fractionally precipitate it by gradual addition of EtOH or 4M NaCl. The resulting gels are centrifuged off, washed with aqueous EtOH or acetone, and dried under vacuum. [Büchner et al. J Chem Soc 3974 1961.] Sodium n-alkylsulfates. Recrystallise these salts from EtOH/Me2CO [Hashimoto & Thomas J Am Chem Soc 107 4655 1985].